Heretofore, fluid pressure devices have been used as actuating mechanisms for transporting and positioning workpieces, and for driving various types of industrial machines. As one such fluid pressure device, in Japanese Laid-Open Patent Publication No. 10-002304, the present applicant has proposed a fluid pressure device equipped with a piston, which is displaceable under a pressing action from a pressure fluid.
The fluid pressure device comprises a piston, which is displaceable inside of a tubular shaped cylinder body, with a piston rod being connected to the piston. In addition, both ends forming openings of the cylinder body are closed respectively by cover members. Further, a piston rod penetrates through a hole provided in one of the cover members, wherein the cylinder body is maintained in an airtight condition by a packing member installed on the inner circumferential surface of the hole. Furthermore, the piston rod is slidably held through means of a bush. On the other hand, o-rings are installed into annular grooves on the cover members, so that through abutment of the o-rings against the inner wall surface of the cylinder body, the interior of the cylinder body is kept airtight.